Graham Stuart Thomas, a horticulturalist, author and botanical artist who was considered by many garden experts as one of the most influential gardeners of the 20th century, died April 17 in a hospital near his home in Woking, south of London. He was 94 and had been hospitalized with pneumonia.
In his eight decades as a "plantsman," Thomas retrieved a number of flower varieties from extinction and restored the grounds of more than 100 historic houses when he served as advisor to the National Trust, a preservationist group in Britain.
A graceful and informative writer, Thomas published 19 books on plants, which he illustrated with his own watercolors and drawings. Most often he wrote about roses, starting with "Old Shrub Roses" (1955). The book was the result of several decades spent collecting and propagating so-called old roses that he acquired from private homes and plant nurseries throughout Europe. By the end of the Edwardian era, those roses had fallen out of fashion in favor of more prolific hybrids.
"Thomas set about preserving the heritage of old roses when many of them were on the verge of extinction," said Clair Martin, rose curator at the Huntington Botanical Gardens in San Marino.
"There were several hundred examples of them between 1800 and 1850, but only a few by the time he began to collect and restore them," Martin said. "He established a baseline on the subject. To learn the history of a particular rose, or how it grows, I refer to his books."
Experts also credit Thomas for his work in perennials, alpine plants, groundcovers and decorative shrubs. His books on those topics are standard references.
"Any serious gardener will tell you that his 'Perennial Garden Plants' (1976) is the most useful thing in their potting shed," said Ngaere Macray, publisher of Sagapress in Long Island, N.Y., a friend of Thomas for more than 20 years. She reissued a number of his early books and also published his most recent: "The Garden Through the Year," written when he was 93. (The books are distributed by Timber Press.)
"Graham probably knew the characteristics of more plants than anyone has ever known," Macray told The Times this week. In an appendix to "The Complete Flower Paintings" (1987), Thomas identifies the more than 600 plants he had propagated by then.
Thomas was born in Cambridge, England, in 1909 into a family of amateur gardeners and musicians. He sang with a madrigal group for 40 years.
